Friday, March 21, 2014

The leak detector is up and running! After draining,flushing, and filling the roughing vacuum pump and cleaning the liquid nitrogen trap, we put the system back online.

Once all that was done, I found out something else that's very cool! You can make your system leak in a calibrated manner to test the leak detector! The gadget for doing this is called a calibrated leak! I'd read about these in the documentation, but never expected to actually see one in the field! Here's a picture

The calibrated leak is the silver cylinder with the white label in the center of the picture. A few weeks ago when the I first started playing with the leak detector[1], I mentioned that it detects leaks by looking for helium using a built-in atomic mass spectrometer. The calibrated leak has a small container of helium that is released at a calibrated rate into the vacuum system once the black valve at the bottom is opened. After that, the leak detector gauge reads the rate at which helium is being introduced into the system and makes a noise very similar to what you might you might expect to hear from a Geiger counter. When the valve is first opened, the leak rate meter rails and the clicks from the audible detector ramp way up as the excess helium behind the valve is released. After a second or so, the clicks even out to a nice constant rate and the meter settles back down reading the rate of the constant leak attached to the system.